Photoflash lamp



Nov. 18, 1947.- H. D. BLAKE ETAL 2,431,162

PHOTOFLASH LAMP Filed Feb. 2, 1945 INVENTORS: HAROLD D. BLAKE, WALTER J.GEIGER,

THEIR ATTORNEY Patented Nov. 18, 1947 PHOTOFLASH LAMP Harold D. Blakeand Walter J. Geiger, Cleveland Heights, Ohio, assignors to GeneralElectric 'Company a corporation of New York Application February 2,1945, Serial No. 575,784

Claims. (CI. 67-31) This invention relates to flash lamps, andespecially to lamps in which a more or less compact mass of closelyassociated combustible and combustion-supporting materials iselectrically ignited, usually by means of an electrically heatedfilament or bridge-wire. Such lamps are much used for photographicpurposes. The combustion mass or body may in turn ignite thin metal foilor fine metal wire, in an oxygenous atmosphere, which by its combustionprovides some or most of the actinic light or radiation from the lamp asin U. S. Reissue Patent No. 18,678 to Ostermeier; or the combustion massmay itself be relied on for most or substantially all of such radiation,as in U. S. Patent No. 2,291,983 to Pipkin. We have hereinafterexplained our invention with particular reference to lamps of thislatter type, which are commercially known as "SM photoflash lamps.

For many photographic purposes, a very quick flash of very high peakintensity is desirable. The requirements are so exacting that commonvariations in commercial grades of combustion materials often render thelamps too slow, or too low in peak intensity, or both; and minorvariations in manufacturing procedure which are very difficult to avoidmay have a similar effect. However, we have found a way of obviatingsuch defects so as to assure adequate quickness and intensity of flashdespite the variations in materials and procedure. We have discoveredthat by suitable treatment during manufacture, the action can be soimproved that the variations whose effects have heretofore been sounfavorable are of no practical consequence. As hereinafter described,the treatment is rather selective in its effects: 1. e., it improvespoor lamps more than good ones, thus evening up the level of quality.

As explained in the above-mentioned Pipkin patent, the combustion bodiesof SM type flashlamps consist of finely divided combustible material andoxidizing material intimately associated or mixed together, andagglomerated or agglutinated by means of a binder. Suitable combustiblesinclude powders of metals like zirconium, magnesium or aluminum; andsuitable oxidizing agents or supporters of combustion are exemplified byoxides or peroxides, and by chlorates including perchlorates. Bindersare exemplified by nitrocellulose, which may be used in the form ofabout a 4% solution in amyl acetate. As mentioned in the Pipkin patent,one suitable composition of the combustion body for a fast lamp, givinga quick, short flash of high intensity, consists of:

Zirconium metal powder grams 3 Magnesium metal powder (325 mesh) do 1Sodium chlorate powder (C. P., 200 mesh) grams; 1 Potassium perchloratepowder (C. P., 300

mesh) grams 1 4% solution of nitrocellulose in amyl acetate cc 2 A lampcomprising a bead of 50 to grams of this composition and having afilling of oxygen at an absolute pressure of about mm. of mercury givesa total light output of about 5000 lumen-seconds and a flash of some 10milliseconds duration, the peak occurring about 5 milliseconds afterclosure of the circuit through the filament.

We have found that the fiash of lamps of this character can besubstantially intensified and quickened by treatment usually involving adeposit of oxidizing agent or supporter of. combustion at the surface ofthe combustion body, generally in the form of crystals more or lessisolated or spaced apart. One way of treating the combustion body is toexpose the mount including said body to a humid atmosphere: e. 3., suchmounts may be kept in ahumidity box at about 100 F. for about 30 min.Another way is to immerse the body in an aqueous solution of solubleoxidizing agent: e. g., such a body may be dipped for about 2 min. in asaturated solution of sodium chlorate at F. Variations in thistemperature of'as much as 10 F. either way are not importantlyinfluential on theresult. For this mode of treatment, a sodium chloratesolution has given better results than a potassium perchlorate solution.In the caseof slow, low-peaking lamps, the improvement may increase thepeak intensity about 50 to 100%, with a decrease of 50% or more in theinterval required to reach the peak after closing the circuit. Aftertreatment of the mounts in either way, they are sealed. into the lampbulbs or envelopes, and the lamp processing iscompleted (includingintroduction of oxygen or other oxygen-containing gas) in the usual way.

In both methods of treatment, it is probable that some of the solublecombustion agent (especially the highly soluble sodium chlorate) isdissolved or leached out of the combustion body.

leaving the latter somewhat porous with increased surface exposure tothe oxygenous atmosphere, This naturally tends toward faster and morecomplete combustion, and mayeven be a major factor in the improvement.There is no material decrease in'the total combustion-supporting contentof the body in either case, since matter dissolved out is more or lesscompensated for by matter deposited on the surface of the body.

In the drawings, Fig. l is a side view of a short bulb neck 3, which ismounted in an ordinary bayonet base 4 to whose contact terminals areconnected the inleads 5, 5 through the usual stem-press seal 6. Anexhaust tube 1 opening through the seal 6 is itself sealed ofi at 8.Between the inner ends of the leads 5, 5 is connected the usual ignitingfilament or bridge-wire 9, and

' on the ends of these leads are shown bead-like bodies I0, In ofcombustion material, each in contact with the filament 9. Broadly,however, it is immaterial whether the bodies I0, 10 are distinct fromone another or merge in a single large bead, as shown in the above-citedPipkin patent. The glass bulb I may have the usual internal or externalcoating (preferably both) of transparent or radiation-transmittinglacquer or varnish, and may contain the usual filling of oxygen'at 100mm. mercury pressure absolute. On the bead surfaces are shownprominences or protuberances formed by isolated white crystal depositsii of oxidizing agent such as sodium chlorate, which look like fine,circular, rounded white specks. As shown, one of the inleads 5 may carrya fine antenna wire l2 welded thereto and extending nearly to the top ofthe bulb, as in U. S. Patent 2,342,575 to Elmendorf.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. The combination with a flash lamp mount comprising an ignitingfilament and a porous body of agglutinated combustible metallic materialand supporter of combustion for liberating oxygen in contact withsaidfilament, of a rough crystal-like deposit of supporter of combustionon the surface of said body.

2. The combination with a flash lamp mount comprising an ignitingfilament and a porous body of agglutinated combustible metallic materialand supporter of combustion for liberating oxygen in contact with saidfilament, of a. rough deposit of soluble chlorate on the surface of saidbody.

3. The combination with a flash mount comprising an igniting filamentand a porous body of agglutinated combustible metallic material andsupporter of combustion comprising chlorate in contact with saidfilament for liberating oxygen upon energization of the filament, ofisolated chlorate crystals adherent to the surface of said body.

4. A flash lamp mount comprising an igniting filament and a porous bodycomprising agglutinated combustible metallic material and solublesupporter of combustion in contact with said filament for liberatingoxygen upon energization of the filament. characterized by pores in saidbody formed by leaching out of soluble supporter of combustion.

5. A fiash lamp mount comprising an igniting filament and a'porous bodyof agglutinated combustible metallic material'and supporter ofcombustion comprising sodium chlorate in contact with said filament forliberating oxygen upon energization of the filament, characterized bypores and prominences formedby leaching out of the sodium chlorate andby isolated deposits of sodium chlorate adherent to the surface of saidbody.

6. A fiash lamp comprising a container, an igniting filament in saidcontainer, and a porous body of agglutinated finely divided combustiblemetallic material and soluble supporter of combustion in contact withsaid filament for liberating oxygen upon energization of said filament,characterized by pores in said body formed by leaching out of solublesupporter of combustion and isolated deposits of soluble supporter ofcombustion adherent to the surface of said body, and an oxygenousatmosphere in said container, the combustible of said body constituting,in coaction with said atmosphere and the supporter of combustion ofthebody, the sole source of actinic radiation from the lamp.

7. A method of intensifying and speeding up the illumination from aflashlamp comprising an igniting filament and a body of agglutinatedcombustible metallic material and soluble supporter of combustion incontact with said filament, which method comprises leaching said bodyand forming a rough crystal-like deposit of the supporter of combustionon the surface of said body.

8. A method of improving the illumination from a, fiashlamp comprisingan igniting filament and a body of agglutinated combustible andsupporter of combustion in contact with said filament, which methodcomprises immersing said body in a solution of soluble supporter ofcombustion until adherent crystals of the latter form on said body.

9. A method of improving the illumination from a fiashlamp comprising anigniting filament and a body of agglutinated combustible and solublesupporter of combustion in contact with said filament, which methodcomprises exposing said body to a humid atmosphere until adherentcrystals of said soluble supporter of combustion form on said body.

10. A method of intensifying and accelerating the illumination from afiashlamp comprising an igniting filament and a body of agglutinatedcombustible metallic material and a soluble supporter of combustion incontact with said filament for liberating oxygen upon energization ofthe filament, which method comprises providing said body with a poroussurface holding adherent particles of the supporter of combustion.

HAROLD D. BLAKE. WALTER J. GEIGER.

REFERENCES CITED UNITED STATES PATENTS Name Date Bostwick Nov. 30, 1897Number

